Steel Fuel Tanks Will Meet the California Air Resources Board (CARB) LEV III Standards

In 2011, California’s Air Resource Board (ARB) is expected to finalize new exhaust and evaporative emission regulations under its LEV III standards which will take effect in 2014 with complete phase-in by 2022.

Although the most restrictive evaporative emission levels will remain the same in LEV III, as in LEV II, ARB has stipulated that the test fuel used for evaporative emission compliance testing will be changed from essentially pure gasoline to a fuel containing 10% ethanol. ARB is making this change because E10 fuels are widely available in California and better represent ‘typical fuels’ used by Californians.

Because steel fuel tank walls are impermeable to hydrocarbons, there will be essentially no changes in emissions when E10 fuel is used and no difficulty in meeting ARB’s rigid evaporative emission limits with the new test protocol! (Steel tanks tested with the current LEV II fuel (CP2) are able to achieve ARB’s limit of 54 mg/hr comfortably).

As the above bar graph shows there is no dependence of tank size on permeation. This is not true for plastics where as tank size (volume) increases the amount of permeation increases.